Search found 60 matches
- Sun Mar 10, 2019 10:08 pm
- Forum: General Rate Laws
- Topic: integrals
- Replies: 8
- Views: 993
Re: integrals
They will be provided but it's good to know how to do them to understand the concepts fully
- Sun Mar 10, 2019 10:06 pm
- Forum: General Rate Laws
- Topic: Units for Rate Constants
- Replies: 5
- Views: 558
Re: Units for Rate Constants
mol/L and then 1/mol/L for second order
- Sun Mar 10, 2019 6:22 pm
- Forum: General Rate Laws
- Topic: how to determine the rate law
- Replies: 2
- Views: 247
Re: how to determine the rate law
Its a direct relationship, so increase in temp results in a faster rate and a decrease in temp results in a slower rate
- Sun Mar 10, 2019 6:20 pm
- Forum: General Rate Laws
- Topic: Rate constant k
- Replies: 3
- Views: 460
Re: Rate constant k
rate constant k determines how fast/slow the reaction occurs using the initial concentrations of the reactants
- Sun Mar 10, 2019 6:17 pm
- Forum: General Rate Laws
- Topic: Rate Determining Step
- Replies: 5
- Views: 2967
Re: Rate Determining Step
Yes, because the slowest rate is essentially the rate law used.
- Sun Mar 10, 2019 6:16 pm
- Forum: General Rate Laws
- Topic: Writing Rate Laws
- Replies: 3
- Views: 455
Re: Writing Rate Laws
Rate laws only focus on the reaction hence why only the concentrations of the reactants matter.
- Sun Mar 10, 2019 6:16 pm
- Forum: General Rate Laws
- Topic: Rate Laws
- Replies: 8
- Views: 722
Re: Rate Laws
Pretty sure they're given but it's good to know how to do it yourself so you understand the concept
- Sun Mar 10, 2019 6:15 pm
- Forum: General Rate Laws
- Topic: Reaction Order
- Replies: 5
- Views: 593
Re: Reaction Order
It depends on the exponents
- Sun Mar 10, 2019 6:14 pm
- Forum: General Rate Laws
- Topic: writing rate laws
- Replies: 4
- Views: 462
Re: writing rate laws
rate of consumption is more specific but are essentially calculated in the same way. however it could have a different sign than the general rate law if it is specific to the reaction
- Sun Mar 10, 2019 6:12 pm
- Forum: General Rate Laws
- Topic: Rate constant k
- Replies: 5
- Views: 611
Re: Rate constant k
k is used to symbolize the rate the chemical reaction is going related to the concentration of reactants and products.
- Tue Feb 19, 2019 6:18 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G a state function?
- Replies: 23
- Views: 2843
Re: Delta G a state function?
Yes it's a state function because it involves entropy and enthalpy
- Tue Feb 19, 2019 6:17 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Equilibrium
- Replies: 3
- Views: 373
Re: Equilibrium
At equilibrium, free energy equals 0, which means g=0
- Tue Feb 19, 2019 6:16 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: What to do when temperature isn't given
- Replies: 8
- Views: 899
Re: What to do when temperature isn't given
It's usually always in standard condition which means 25C or 298K
- Mon Feb 11, 2019 12:10 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard reaction enthalpy vs standard enthalpy of formation
- Replies: 2
- Views: 374
Re: Standard reaction enthalpy vs standard enthalpy of formation
Standard reaction enthalpy is the enthalpy that occurs in a reaction and the SE of formation is during the formation of 1 mole of something
- Mon Feb 11, 2019 12:08 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Open vs Closed System
- Replies: 13
- Views: 4594
Re: Open vs Closed System
In a closed system, matter must stay fixed, but an open system is more flexible
- Mon Feb 11, 2019 12:07 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units for enthalpy
- Replies: 6
- Views: 753
Re: Units for enthalpy
I think the SI unit is kJ and is used as the final answer on most of the answer keys, so it would be safer to put the final answer in kJ
- Mon Feb 11, 2019 12:06 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy of Phase Changes
- Replies: 4
- Views: 411
Re: Enthalpy of Phase Changes
The enthalpy from liquid to gas is higher because in addition to raising the temperature, more heat is required to separate the molecules to a gas
- Mon Feb 11, 2019 12:05 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpies of Formation
- Replies: 3
- Views: 350
Re: Standard Enthalpies of Formation
He will most likely put the specific standard enthalpy we need in the question
- Mon Feb 11, 2019 12:04 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 5
- Views: 533
Re: Hess's Law
I think the test will provide them for us, according to my TA
- Mon Feb 11, 2019 12:03 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Conversions
- Replies: 4
- Views: 473
Re: Conversions
The L*atm to Joules will probably be needed since we use it most in problems but everything else is on the equation sheet
- Mon Feb 11, 2019 12:03 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond enthalpies
- Replies: 10
- Views: 920
Re: Bond enthalpies
You don't need to know the lewis structures for the midterm, but my TA said it was easier to visualize if you drew out the Lewis structure
- Mon Feb 11, 2019 12:01 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Explaining Hess's Law with enthalpy = a state function?
- Replies: 3
- Views: 421
Re: Explaining Hess's Law with enthalpy = a state function?
Enthalpy is a state function, so it doesn't matter what path it takes, as long as it reaches enthalpy
- Mon Feb 11, 2019 12:01 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Homework during midterm week [ENDORSED]
- Replies: 5
- Views: 474
Re: Homework during midterm week [ENDORSED]
Any first law or second and third law of thermodynamics problems I'm pretty sure
- Mon Feb 11, 2019 11:59 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: cooling a system
- Replies: 3
- Views: 394
Re: cooling a system
Endothermic: reaction will lean towards reactant
Exothermic: reaction will lean towards products
Exothermic: reaction will lean towards products
- Mon Feb 04, 2019 11:30 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: PV=nRT
- Replies: 5
- Views: 533
Re: PV=nRT
It can only be used on idea gases
- Mon Feb 04, 2019 11:28 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Material on Midterm?
- Replies: 9
- Views: 877
Re: Material on Midterm?
Yeah it goes until the end of enthropy
- Mon Feb 04, 2019 11:27 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: reaction constant P
- Replies: 3
- Views: 340
Re: reaction constant P
It only works for gases because pressures only affect gases and not solids or liquids
- Mon Feb 04, 2019 11:19 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 2nd law of thermodynamics
- Replies: 5
- Views: 575
Re: 2nd law of thermodynamics
Entropy increases, and as the amount of energy used decreases, the amount of energy not used increases
- Mon Feb 04, 2019 11:17 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: enthalpy of combustion vs formation
- Replies: 3
- Views: 539
Re: enthalpy of combustion vs formation
The enthalpy of combustion is the energy released as heat when the reaction undergoes combustion. Standard enthalpy of formation is the change of enthalpy when exactly 1 mole of compound is formed.
- Mon Feb 04, 2019 11:14 pm
- Forum: Calculating Work of Expansion
- Topic: Difference between reversible and irreversible expansion?
- Replies: 2
- Views: 882
Re: Difference between reversible and irreversible expansion?
A reversible reaction is more efficient because the volume changes very slowly and can easily be manipulated to reach equilibrium. However, an irreversible reaction moves very fast and uses large amounts, so it is harder to reach equilibrium easily, so therefore it is irreversible.
- Mon Feb 04, 2019 11:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Midterm
- Replies: 12
- Views: 2161
Re: Midterm
I think there's one next Monday
- Fri Nov 30, 2018 12:57 am
- Forum: Hybridization
- Topic: Lone Pairs in hybridization
- Replies: 3
- Views: 448
Re: Lone Pairs in hybridization
Lone pairs needed to be accounted for in hybridization
- Fri Nov 30, 2018 12:56 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: test #3
- Replies: 14
- Views: 1540
Re: test #3
Paramagnetic means that there is one electron in the subshell, and diamagnetic means that there are two paired electrons with opposite spin in the same subshell.
- Thu Nov 29, 2018 2:05 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Ionic Character
- Replies: 3
- Views: 375
Re: Ionic Character
Knowing how electronegative an element is helps with determining whether there are ionic or covalent bonds, and if covalent, whether they are polar or non-polar.
- Thu Nov 29, 2018 2:03 am
- Forum: Resonance Structures
- Topic: Hybrid Resonance
- Replies: 4
- Views: 669
Re: Hybrid Resonance
It's the average of all of the possible resonance structures which determines the structure
- Thu Nov 29, 2018 2:00 am
- Forum: Resonance Structures
- Topic: Labelling Resonance Structures
- Replies: 3
- Views: 510
Re: Labelling Resonance Structures
I don't think it's necessary either
- Thu Nov 29, 2018 2:00 am
- Forum: Resonance Structures
- Topic: Drawing resonance
- Replies: 17
- Views: 1895
Re: Drawing resonance
Even if it isn't required to draw all of the resonance structures, it's probably helpful in the long run to just draw them all out on tests and homework.
- Thu Nov 29, 2018 1:58 am
- Forum: Resonance Structures
- Topic: Bond lengths & number of resonance structures
- Replies: 3
- Views: 658
Re: Bond lengths & number of resonance structures
The average number of resonance structures determine the shape, therefore it is an average number of bond lengths.
- Thu Nov 29, 2018 1:56 am
- Forum: Coordinate Covalent Bonds
- Topic: bound atoms vs separate atoms
- Replies: 5
- Views: 809
Re: bound atoms vs separate atoms
Free moving atoms have more potential energy therefore are more unstable. Bound atoms have less potential energy because they are bound, so they are more stable than the free moving atoms.
- Thu Nov 29, 2018 1:48 am
- Forum: Lewis Structures
- Topic: Lewis structure for POCl3
- Replies: 7
- Views: 1374
Re: Lewis structure for POCl3
Phosphorus is unique in that it has an expanded octet and is also the least electronegative which is why it is the central atom.
- Thu Nov 29, 2018 1:37 am
- Forum: Sigma & Pi Bonds
- Topic: Why are sigma bonds stronger than pi bonds?
- Replies: 10
- Views: 4712
Re: Why are sigma bonds stronger than pi bonds?
The greater overlap in the sigma bonds makes it stronger than the pi bonds.
- Thu Nov 29, 2018 1:34 am
- Forum: Ionic & Covalent Bonds
- Topic: Strength of Bonds?
- Replies: 5
- Views: 681
Re: Strength of Bonds?
Ionic bonds are stronger due to their particular ionic character. And polarization power depends in covalent bonds.
- Sun Nov 11, 2018 4:58 pm
- Forum: Lewis Structures
- Topic: Molecule Shape
- Replies: 8
- Views: 777
Re: Molecule Shape
VSPER allows you to tell the shape of the structure
- Sun Nov 11, 2018 4:55 pm
- Forum: Lewis Structures
- Topic: Atoms with 8+ valence e-
- Replies: 6
- Views: 1021
Re: Atoms with 8+ valence e-
D and f subshells can account for more than 8 electrons, therefore the expanded octet.
- Sun Nov 11, 2018 4:53 pm
- Forum: Lewis Structures
- Topic: Lewis Structure
- Replies: 10
- Views: 848
Re: Lewis Structure
Make sure that the Lewis structure adds up to the amount of valence electrons and there are all complete octets and the formal charges all around are zero.
- Sun Nov 11, 2018 4:51 pm
- Forum: Ionic & Covalent Bonds
- Topic: delta positive delta negative
- Replies: 15
- Views: 2339
Re: delta positive delta negative
Delta negative: accepts electrons
Delta positive: donates electrons
Delta positive: donates electrons
- Sun Nov 11, 2018 4:17 pm
- Forum: Ionic & Covalent Bonds
- Topic: Chemical Bonds
- Replies: 5
- Views: 562
Re: Chemical Bonds
Ionic bonds are shorter because they are stronger bonds
- Sun Nov 11, 2018 4:11 pm
- Forum: Ionic & Covalent Bonds
- Topic: Strength of Bonds?
- Replies: 5
- Views: 681
Re: Strength of Bonds?
Covalent bonds share electrons
- Sun Nov 11, 2018 4:09 pm
- Forum: Ionic & Covalent Bonds
- Topic: Proportionality of bond strength
- Replies: 3
- Views: 533
Re: Proportionality of bond strength
Although the number of bonds increase bond strength, you also have to consider the bond lengths, therefore, it isn't just completely linear from a single to double bond
- Sun Nov 11, 2018 4:08 pm
- Forum: Ionic & Covalent Bonds
- Topic: Metallic Bond
- Replies: 7
- Views: 682
Re: Metallic Bond
Bonding between two metal ions
- Sun Nov 11, 2018 4:07 pm
- Forum: Ionic & Covalent Bonds
- Topic: Van der Waals vs Dispersion Forces
- Replies: 8
- Views: 1182
Re: Van der Waals vs Dispersion Forces
They are both intermolecular forces that are relatively weak
- Sun Nov 11, 2018 2:39 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Geometric Shape and Bond Angle
- Replies: 3
- Views: 538
Re: Geometric Shape and Bond Angle
The shape is determined by how the atoms are arranged
- Sun Nov 11, 2018 2:37 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSPER and bond strength
- Replies: 2
- Views: 162
Re: VSPER and bond strength
Yes, stronger bonds have greater repulsion
- Sun Nov 11, 2018 2:36 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: molecular shapes
- Replies: 13
- Views: 978
Re: molecular shapes
I don't think we have to
- Sat Nov 10, 2018 7:10 pm
- Forum: Ionic & Covalent Bonds
- Topic: Hydrogen bonding
- Replies: 7
- Views: 1357
Re: Hydrogen bonding
H20's bond length is shorter than H2S which means its harder for electrons to break apart, therefore it has a higher boiling point than H2S.
- Sat Nov 10, 2018 7:08 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionization Energies
- Replies: 13
- Views: 3688
Re: Ionization Energies
Yes and it is very hard to release an electron because the electrons are so tightly packed to each other
- Sat Nov 10, 2018 7:00 pm
- Forum: Ionic & Covalent Bonds
- Topic: Dissociation Energy
- Replies: 3
- Views: 385
Re: Dissociation Energy
Dissociation energy is negative when the bond is releasing energy, and it is positive when it is absorbing energy
- Fri Oct 05, 2018 5:25 pm
- Forum: Limiting Reactant Calculations
- Topic: Limiting reagents
- Replies: 12
- Views: 866
Re: Limiting reagents
There cannot be two limiting reactants, because only one can do the limiting to the other. However, there can be no limiting reactants in which the mole ratio for the reactants are equal.
- Fri Oct 05, 2018 5:23 pm
- Forum: SI Units, Unit Conversions
- Topic: formula units [ENDORSED]
- Replies: 69
- Views: 32947
Re: formula units [ENDORSED]
Any ionic or covalent solid compound not just salts
- Fri Oct 05, 2018 5:19 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Rounding molar mass
- Replies: 4
- Views: 325
Re: Rounding molar mass
I would use the molar mass from the periodic table for a more accurate answer and then round the final answer to the number of sig figs that are in the numbers given in the problem.